/* mpfr_mul_ui -- multiply a floating-point number by a machine integer

Copyright 1999-2024 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.

The GNU MPFR Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */

#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"

#undef mpfr_mul_ui
MPFR_HOT_FUNCTION_ATTR int
mpfr_mul_ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int u, mpfr_rnd_t rnd_mode)
{
  int inexact;

  MPFR_LOG_FUNC
    (("x[%Pd]=%.*Rg u=%lu rnd=%d",
      mpfr_get_prec(x), mpfr_log_prec, x, u, rnd_mode),
     ("y[%Pd]=%.*Rg", mpfr_get_prec (y), mpfr_log_prec, y));

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
    {
      if (MPFR_IS_NAN (x))
        {
          MPFR_SET_NAN (y);
          MPFR_RET_NAN;
        }
      else if (MPFR_IS_INF (x))
        {
          if (u != 0)
            {
              MPFR_SET_INF (y);
              MPFR_SET_SAME_SIGN (y, x);
              MPFR_RET (0); /* infinity is exact */
            }
          else /* 0 * infinity */
            {
              MPFR_SET_NAN (y);
              MPFR_RET_NAN;
            }
        }
      else /* x is zero */
        {
          MPFR_ASSERTD (MPFR_IS_ZERO (x));
          MPFR_SET_ZERO (y);
          MPFR_SET_SAME_SIGN (y, x);
          MPFR_RET (0); /* zero is exact */
        }
    }
  else if (u <= 1)
    {
      if (u < 1)
        {
          MPFR_SET_ZERO (y);
          MPFR_SET_SAME_SIGN (y, x);
          MPFR_RET (0); /* zero is exact */
        }
      else
        return mpfr_set (y, x, rnd_mode);
    }
  else if (MPFR_UNLIKELY (IS_POW2 (u)))
    return mpfr_mul_2si (y, x, MPFR_INT_CEIL_LOG2 (u), rnd_mode);

#ifdef MPFR_LONG_WITHIN_LIMB
  {
    mp_limb_t *yp;
    mp_size_t xn;
    int cnt;
    MPFR_TMP_DECL (marker);

    yp = MPFR_MANT (y);
    xn = MPFR_LIMB_SIZE (x);

    MPFR_ASSERTD (xn < MP_SIZE_T_MAX);
    MPFR_TMP_MARK(marker);
    yp = MPFR_TMP_LIMBS_ALLOC (xn + 1);

    MPFR_ASSERTN (u == (mp_limb_t) u);
    yp[xn] = mpn_mul_1 (yp, MPFR_MANT (x), xn, u);

    /* x * u is stored in yp[xn], ..., yp[0] */

    /* since the case u=1 was treated above, we have u >= 2, thus
       yp[xn] >= 1 since x was msb-normalized */
    MPFR_ASSERTD (yp[xn] != 0);
    if (MPFR_LIKELY (MPFR_LIMB_MSB (yp[xn]) == 0))
      {
        count_leading_zeros (cnt, yp[xn]);
        mpn_lshift (yp, yp, xn + 1, cnt);
      }
    else
      {
        cnt = 0;
      }

    /* now yp[xn], ..., yp[0] is msb-normalized too, and has at most
       PREC(x) + (GMP_NUMB_BITS - cnt) non-zero bits */
    MPFR_RNDRAW (inexact, y, yp, (mpfr_prec_t) (xn + 1) * GMP_NUMB_BITS,
                 rnd_mode, MPFR_SIGN (x), cnt -- );

    MPFR_TMP_FREE (marker);

    cnt = GMP_NUMB_BITS - cnt;
    if (MPFR_UNLIKELY (__gmpfr_emax < MPFR_EMAX_MIN + cnt
                       || MPFR_GET_EXP (x) > __gmpfr_emax - cnt))
      return mpfr_overflow (y, rnd_mode, MPFR_SIGN(x));

    MPFR_SET_EXP (y, MPFR_GET_EXP (x) + cnt);
    MPFR_SET_SAME_SIGN (y, x);
    MPFR_RET (inexact);
  }
#else
  {
    mpfr_t uu;
    MPFR_SAVE_EXPO_DECL (expo);

    mpfr_init2 (uu, sizeof (unsigned long) * CHAR_BIT);
    /* Warning: u might be outside the current exponent range! */
    MPFR_SAVE_EXPO_MARK (expo);
    mpfr_set_ui (uu, u, MPFR_RNDZ);
    inexact = mpfr_mul (y, x, uu, rnd_mode);
    mpfr_clear (uu);
    MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
    MPFR_SAVE_EXPO_FREE (expo);
    return mpfr_check_range (y, inexact, rnd_mode);
  }
#endif /* MPFR_LONG_WITHIN_LIMB */
}
